In general, a silicon single crystal is manufactured under high temperature conditions by pulling the crystal from a silicon melt stored in a vitreous silica crucible. Rotation mold method (Patent Reference 1) is known as a method of producing the vitreous silica crucible. In this method, silica powder is deposited on an inner surface of rotating cylindrical mold that has inner space (cavity) and a bottom. The silica powder is fused (molten) at high temperature by arc discharge or the like, vitrified, and is formed to have a shape of a crucible in accordance with the shape of the inner surface of the mold. After cooling, by removing from the mold, a designated crucible is obtained.
A vitreous silica crucible used in a pulling of a silicon single crystal is required to have a high precision in its shape as well as a high purity in the same level as that of a semiconductor. For example, if the wall thickness of the crucible is not constant, even though a charge of polycrystalline silicon is maintained at constant amount, surface level of the silicon melt fluctuates when the polycrystalline silicon is molten. In addition, because of the fluctuation of the melt surface, falling rate of the melt surface compared with the pulling rate is not stable even though the pulling rate is maintained at constant during pulling a silicon single crystal from the silicon melt, thereby causing decrease in the yield of single crystal.
Patent Reference 1 Japanese Patent No. 1257513 (Japanese Patent Publication No. S59-34659).